BaO对单Pd催化剂净化甲醇燃料车尾气性能的影响

利用FIB/SEM切片、XRD、TEM和EDX、EELS等先进分析技术对微球模板法所制备的Au/Ag泡沫材料的微观结构、形貌、成分及成分分布等进行了细致的研究.结果表明:由微球状Au/Ag球壳堆积而成的泡沫材料中微球直径约8 μm,微球壁厚200～1200 nm; Au/Ag泡沫材料的球壳可细分为3层,内层和外层为Au/Ag合金的微粒,中间主要是非晶碳层,夹杂有少量的Au/Ag微粒；Au/Ag泡沫材料的骨架由单个空心球壳组成,球壳之间通过接触点的金属镀层连接在一起；球壳上有小孔状结构,是在热分解法去除聚苯乙烯微球模板对形成的；球壳壁厚分布不均匀,少数球壳有塌陷、变形、破裂等现象.这些详细的分析有助于改进工艺,提高Au/Ag泡沫材料的制备质量.

Effects of BaO on the Performance of Catalytic Purification Exhausts from the Gasoline-Methanol Fuel Over Only-Palladium

Only-Palladium catalysts modified with BaO as a promoter was prepared by an impregnation method. Specific surface area measurements (BET), X-ray diffraction (XRD), CO-chemisorption, H2-temperature-programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the effect of BaO on the physicochemical properties of the catalysts. Their catalytic activities towards methanol, CO and C3H8 conversions were evaluated. The results show that the addition of BaO makes palladium highly dispersed, enhances the amount of active oxygen and promotes the reductive ability. The electron effects between Pd and support is improved. It is favorable for maintaining Pd in a higher oxidized state and transiting Ce4+ to Ce3+, thus accelerating the activated oxygen migration between Pd and the support and consequently increasing the catalytic activities for methanol and CO oxidation at low temperature. The light-off temperature of T50 is lowered by 26 and 21 oC to methanol and CO, respectively compared with unmodified only-Palladium catalysts. Whereas the conversion of C3H8 falls directly because of the higher oxidized Pd2+ and the amount and intensity of the acid sites decreasing obviously